Martin, R. Erik, Robert G. Ernest, Nancy W. Walls 



and J. Ross Wilcox 



Size Distribution and Seasonal Abundance of Loggerhead 

 and Green Turtles in Nearshore Waters off 

 Hutchinson Island. Florida 



Applied Biology, Inc. 

 Jensen Beach, Florida 34958 USA 



Florida Power & Light Company 

 Juno Beach, Florida 33408 USA 



The St. Lucie Power Plant is located on Hutchinson Island in 

 southeast Florida. The plant draws its condenser cooling water 

 through an enclosed intake canal connected with the Atlantic 

 Ocean via submerged pipes. Sea turtles, which are apparently 

 attracted to the offshore structures housing the intake pipes, 

 are often entrained with cooling water and become trapped in the 

 intake canal. Since the plant began operating, entrapped sea 

 turtles have been systematically captured, measured, weighed, 

 tagged and returned to the ocean. 



From May 1976 through December 1986, 1,322 loggerhead and 

 192 green turtles were removed from the St. Lucie Plant intake 

 canal. Loggerheads ranged in size from 41.5 to 112.0 cm (mean = 

 64.9 + 11.9 cm; minimum SLCL) . Seventy-five percent of these 

 were classified as immature (SLCL<70 cm) with the majority in the 

 50-70 cm size classes. Adults (SLCL>80 cm) constituted 12.5 

 percent of total loggerhead captures. A transitional size class 

 (70-80 cm SLCL) containing both immature and mature animals 

 accounted for the remaining 12.5 percent. 



Green turtles removed from the intake canal ranged in size 

 from 20 to 108 cm (mean = 36.9 ± 15.1 cm; minimum SLCL). Ninety- 

 six percent were classified as immature, and 74 percent were 40 

 cm or less in length. 



Immature loggerhead and green turtles were captured with 

 greatest frequency during the winter (January-March) . However, 

 the proportion of juveniles captured during winter was much 

 greater for green turtles than for loggerheads. Adult 

 loggerheads (n = 161) were most abundant during the summer, and 

 adult captures were predominated by females (n = 131) . Five of 

 the six adult green turtles captured were males; all were 

 collected between June and October. 



Size-frequency distributions of loggerhead 

 and green turtles captured at the St. Lucie Plant 

 were compared with those from other locations 

 along the east coast of Florida, Georgia and South 

 Carolina. Collectively these data suggest that: 



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